High on my list of “Biggest Sins Managers Commit When Interviewing” is one that never fails to make me shake my head. People are almost always unaware they’re doing it until I point it out, but even when they recognize they’re guilty, many can’t stop themselves.

What is this widespread transgression? Talking too much in your interviews.

Here’s how it usually unfolds:

In an effort to break the ice at the start of the interview, the hiring manager offers to tell the candidate a little about his or her background and history with the company. Yes, some people provide a brief overview and leave it at that. But far too many others ramble on way too long about when and how they joined the organization, all the positions they’ve held to date, their major accomplishments and proudest moments, all the changes they’ve seen over the years, etc.

And how does this little walk down memory lane help them learn about the candidate? It doesn’t! You can only learn about another person when you’re listening, not when you’re talking. So reminiscing about your past, while undoubtedly fun for you, doesn’t really help you figure out if this person across the table is someone who might be a good fit for your open position.

But once they get on a roll, lots of managers don’t stop there. They soon move on to talking about the company (it’s history, it’s current activities and projects, it’s goals and plans) and the job (what the position entails, what type of person they’re looking to hire for it, why they think it’s a great opportunity). And before you know it, guess what they’ve done?

They’ve given the candidate all the answers to the test they’re about to take. How so? Because anyone who knows anything about interviewing will take all that helpful information the manager just provided and use it to frame their answers in a way that makes them the perfect fit for the company and the job. This is one of the primary ways managers get fooled and end up making a bad hiring decision.

“But, he told me negotiating pricing was one of his strengths and that he didn’t mind traveling a couple of days a week. He also said he’d be happy in a small, stable company that didn’t have plans to grow or expand in the near future. None of these things ended up being true, and I can’t figure out why he said what he did.”

My guess is because you’d pretty much already told him what you wanted to hear, and he was smart enough to play it back to you. This is why managers often end up feeling like the person they interviewed and the person who ultimately comes to work for them are two entirely different individuals.

So, what can managers do to avoid this unpleasant scenario? Adhere to the 80/20 rule.

In an interview, the candidate should do 80 percent of the talking, and the interviewer should do 20 percent. If you’re the hiring manager, this means you’ll need to use your 20 percent for asking questions that get candidates to open up and shed some light on their strengths, weaknesses, and preferences. You can’t use your allotment for talking about yourself or your company or your open position. Certainly you can talk a little about those topics, but not nearly as much as you probably have in the past. Hit the highlights and move on.

You’ll learn a lot more that way.

Think about the interviews you’ve conducted in the past. Are you guilty of talking too much? Can you identify times when doing so had a negative impact on your hiring decision? Please share your experiences in the comments section.

Janna Mansker is vice president of client services for Berke, a human resources consulting firm, where she leads the company’s education initiatives and advocates for clients. She can be reached at janna@berkegroup.com.